The present invention broadly relates to a camera, more particularly, relates to an auto-focus camera.
An auto-focus camera has been known which employs a stepping motor which operates in accordance with the result of photometry so as to drive a shutter device for controlling the exposure time and to control the lens drive to extend or retract the taking lens.
More specifically, since an auto-focus camera usually incorporates a microcomputer, various controls performed in accordance with data obtained through various sensors are preferably conducted digitally, and this is a reason why a stepping motor is preferably used.
Accordingly, such an auto-focus camera is required to incorporate a power supply for driving the stepping motor It has been experienced that the power supply is accidentally turned off during driving of motors. It is also experienced that the initial rotational phase of the stepping motor is deviated for some reasons from the correct initial set position. If the photographer is not aware of occurrence of such an error, undesirable effects are caused such as a significant exposure error or a large amount of defocus.
Erroneous operations of lens and shutter are also caused by various other reasons such as omission of a pulse from a driving pulse train resulting in a phase offset of the stepping motor, even when the initial rotational phase of the stepping motor is set correctly. Erroneous operation is also caused due to a trouble in a mechanical linking system or a defect in a magnet which is used for setting the lens in the in-focus position.
On the other hand, cameras are known which are capable of informing the user of the occurence of erroneous operations.
However, these known cameras can inform the user of only the occurence of erroneous operations but can not automatically stop driving of the lens and reset the lens at the initial position. Also, these known cameras can not automatically suspend the photography operations when an erroneous operation occurs.
Furthermore, since these known cameras have many sensors corresponding to many detection objects, i.e., various motions or mechanisms to be monitored, the number of parts is undesirably increased. Accordingly, these known cameras fail to meet the demand for reduction in the size and cost.